Mild Cognitive Impairment in Parkinson’s Disease

Abstract

Cognitive impairment is integral to Parkinson’s disease (PD). Most non-demented PD patients show some degree of CI that eventually progresses to dementia in up to 80 % of surviving patients. The term mild cognitive impairment (MCI) has been applied to a transitional stage between normal aging and dementia. MCI can be identified in up to 28 % of non-demented PD patients and has been observed from the early stages of the disease. While frontal-related attentional-executive and recall memory deficits are predominant in most PD patients at the initial stages of the disease, the passage from MCI to dementia appears heralded by a change in the neuropsychological pattern of disturbances with the addition of alterations in cognitive domains (recognition memory, visuospatial, language) more dependent on the dysfunction of the temporal lobe and posterior cortical areas. Neuroimaging findings also support the importance of structural changes in the medial temporal lobes in the progression to dementia. Most studies of MCI in PD have been hampered by lack of standardized diagnostic criteria challenging the definition of the natural course of cognitive decline from normal cognition to MCI and later dementia. Following recent recommended criteria to diagnose PD-MCI should facilitate a better definition of the trajectory of cognitive impairment in PD and its risk factors as well as the design of upcoming therapeutic trials.